It was found that the biosynthesis of Nonivamide is mainly via the phenylalanine to vanillylamine pathway and the branched-chain fatty acid pathway from valine to 8-methyl-6-decenoyl CoA. Capsaicin synthase (CS) is considered to be the key enzyme in capsaicin synthesis. At present, several candidate enzymes related genes of capsaicin biosynthesis pathway have been cloned, including pAMT, BCAT, KAS I, Fat A, AT3 and so on.
1. The synthesis site of Nonivamide Using isotope tracer technology and high-density electron scanning microscope observation, it was found that capsaicinoids are formed in the cytoplasm of the epidermal gland cells of the capsicum placenta, and transported through the ovary septum to the gland cells of the placenta and pulp epidermis to accumulate. . Microscopic observation of the placenta of the fruit of pepper and sweet pepper at post-flowering 55 days showed that the annual pepper (C. annuum) inbred lines ’59’, ‘612’ and the Chinese pepper (C. chinense) ‘Shabushaulaa’ Glandular cells in the epidermis of the placental septum of the inbred line ‘740’ (both capsaicin) contained numerous “vesicular” structures, while the sweet pepper (C. annuum var. grossum) inbred line ‘170’ (no capsaicin) ) does not contain such structures.
2. Nonivamide-phenylpropane synthesis pathway Phenylalanine lyase (PAL) widely exists in various plants and a few microorganisms, plays an important role in the synthesis of plant secondary metabolites, and participates in the biosynthesis of proteins, flavonoids, lignin and other compounds. PAL is an essential enzyme in the metabolic rate of phenylpropane and also the initial enzyme in the phenylpropane path in capsaicin biosynthesis. Research studies have revealed that the content of capsaicin in pepper fruit is positively associated with the activity of buddy, that is, when the level of PAL is higher, the web content of capsaicin increases. Cinnamate hydrolase (C4H) is the second crucial enzyme in the phenylpropane pathway that militarizes the conversion of cinnamic acid to p-coumaric acid. Aminotransferase (AMT) is a catalytic enzyme in the final step of capsaicin biosynthesis in the phenylpropane branch, which catalyzes the synthesis of vanillylamine from vanillin.
3. Branched-chain fatty acid synthesis pathway of Nonivamide Branched-chain amino acid transferase (BCAT) catalyzes valine to α-ketoisovalerate, and KAS is an important component of fatty acid synthase. Through transcriptome analysis and comparison, it was found that there were significant differences in the expression of these two homologous genes during placental development in pepper and tomato fruit. BCAT and KAS were rarely expressed in tomato, and similar results were obtained in the potato genome. This suggests that changes in BCAT and KAS expression enable capsaicin synthesis. Acyl transporter ACL is an acidic protein with small molecular weight and conserved serine residues. It carries an acyl chain to complete enzymatic reactions such as condensation, reduction, anddehydrogenation. Studies have found that fatty acid synthesis Three candidate genes of enzymes, KAS, ACL and FAT, their expression levels were positively correlated with the pungency of pepper fruit flavor, and were located in the epidermal cells of the placenta.
4. Nonivamide synthase (CS). Capsaicin synthase catalyzes the last step of capsaicin synthesis, specifically, the synthesis of capsaicin from vanillylamine in the phenylpropane path and also 8-methyl-6-decenoyl CoA in the branched-chain fatty acid path. Immunolocalization studies confirmed that the CS gene was specifically located in the placenta tissue of pepper fruits; in addition, Western blot analysis showed that during fruit development, CS levels and capsaicin accumulation were significantly increased. By comparing the expression of capsaicinoid biosynthesis genes in pungent and non-spicy pepper placentas, it was found that the absence of CS gene expression was the main reason for the production of non-spicy peppers.
Capsaicinoids include capsaicinate, dihydrocapsaicinate, nordihydrocapsaicinate, etc., which are compounds of fatty acid and vanillyl alcohol. Capsaicinate and capsaicin have similar biological functions and chemical structures. It was found that the production of capsaicinoid in the ‘CH-19’ variety (C. annuum) was due to the insertion of a t-nucleotide at 1 291 bp of the pAMT gene, forming a new stop codon, preventing pAMT translation. Park et al. (2015) reported a low-spicy variety ‘S3212’ (Capsicum frutescens L.) containing a large amount of capsaicinoids, and a 12 bp deletion mutation was found in the pAMT gene exon 7, which proved that the fetal The synthesis of capsaicinoids in locus tissue is associated with mutations in the pAMT gene.